We evaluated the immunohistochemical staining profile of clusterin in paraffin sections of 143 neoplasms (non-Hodgkin lymphoma, 83, including 41 anaplastic large cell lymphomas [ALCLs]; Hodgkin lymphoma, 17; primary and metastatic carcinoma, 30; and other neoplasms, 13). In 40 of 41 ALCLs (34 systemic, 7 cutaneous), neoplastic cells revealed clusterin reactivity characterized by a Golgi staining pattern. The proportion of reactive cells varied with more than 25% positive cells in the majority of cases. In 7 non-Hodgkin lymphomas of other types, fine cytoplasmic (3 cases) or strong membranous reactivity (4 cases) was observed for clusterin. In Hodgkin lymphoma, rare Reed-Sternberg cells exhibited focal cytoplasmic or membranous clusterin positivity. In the nonhematopoietic neoplasms, a Golgi staining pattern was apparent in only 2 cases, 1 lobular carcinoma of the breast and 1 poorly differentiated colonic carcinoma; however, cytoplasmic reactivity was noted in 12 of 30 carcinomas and 1 of 5 neuroendocrine neoplasms. A Golgi pattern of reactivity for clusterin seems highly characteristic of ALCL among hematopoietic neoplasms, but also might be observed in rare nonhematopoietic tumors, necessitating the use of a broad immunohistochemical panel for evaluation of poorly differentiated neoplasms of indeterminate derivation.